Rotary electric machine having resilient fixing cap

ABSTRACT

An upper coil bar and lower coil bar are disposed in slots of an armature core. The upper coil bars have upper coil-end sections which extend radially from the outer periphery of the armature core and together form a commutator surface with which a brush member is in contact. The upper coil-end sections and coil-end sections of the lower coil bars are retained by a fixing cap fixed between a shaft of the rotary electric machine and the upper coil-end sections, and also by a spacer disposed between the upper coil-end sections and the lower coil-end sections so that the commutator surface can be maintained smooth even under conditions of thermal expansion or high-speed operation.

This is a division of application Ser. No. 08/866,573, filed Jun. 2,1997 which was a Continuation of application Ser. No. 08/571,786 filedDec. 13, 1995, now abandoned.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims priority from JapanesePatent Applications Hei 6-310539 filed on Dec. 14, 1994, Hei 6-315330filed on Dec. 19, 1994, Hei 7-25731 filed on Feb. 14, 1995, Hei 7-128645filed on May 26, 1995, and Hei 7-239901 filed on Sep. 19, 1995, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric rotary machine suitable forhigh power and high speed operation, and more particularly relates to astarter for an internal combustion engine.

2. Description of Related Art

U.S. Pat. No. 5,130,596, which corresponds to Japanese Unexamined PatentPublication Hei 2-241346, discloses a rotary electric machine which hasan upper coil of a single turn and a lower coil of a single turn in eachslot of an armature of the armature core are extended from the armaturecore to have a reduced outside diameter of the extended upper coils soas to form a cylindrical commutator held by resinous material, on whichbrushes are disposed in contact therewith.

However, since the commutator of the above electric machine has to holdthe extended upper and lower coils against centrifugal force and thermalstress, it is difficult to keep the commutating surface smooth when themachine is used as a high power machine or high speed machine.

SUMMARY OF THE INVENTION

The present invention is made in view of the above problems, and aprimary object of the present invention is to provide a rotary electricmachine which can be used as a high power and high speed machine.

Another object of the present invention is to provide a rotary electricmachine which has smooth commutator structure of high heat dissipationand of high mechanical strength against centrifugal force and thermalexpansion.

Another object of the present invention is to provide a rotary machinewhich includes a plurality of radially disposed lower coil-end sections,a plurality of radially disposed upper coil-end sections with which abrush member is disposed in contact and means for restricting axialmovement of the upper coil-end sections.

Another object of the present invention is to provide a rotary electricmachine which includes the restricting means having a member to allowcoil sections to expand thermally in a direction opposite the commutatorsurfaces.

Another object of the present invention is to provide a rotary electricmachine which includes the restricting means having a member engagedwith the coil-end sections at one end thereof.

Another object of the present invention is to provide a rotary electricmachine in which the restricting means has a spacer disposed between theupper coil-end sections and the lower coil-end sections.

Another object of the present invention is to provide a rotary electricmachine in which each of the coil sections has projections and thespacer has recesses so that each of the projections is fitted into acorresponding one of the recesses.

A further object of the present invention is to provide a rotaryelectric machine in which the restricting means includes a fixingportion secured to the shaft of the rotary electric machine, a portionbiasing the upper coil-end sections and an elastic portion connectingthe fixing portion and the biasing portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and characteristics of the present invention aswell as the functions of related parts of the present invention willbecome clear from a study of the following detailed description, theappended claims and the drawings. In the drawings:

FIG. 1 is a cross-sectional side view illustrating a rotary electricmachine according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional side view illustrating an armature accordingto the first embodiment;

FIG. 3 is a schematic plan view illustrating the armature core plateaccording to the first embodiment;

FIG. 4 is a perspective view illustrating an upper coil bar according tothe first embodiment;

FIG. 5 is a plan view illustrating the upper coil bar viewed from thefront of the armature according to the first embodiment;

FIG. 6 is a schematic perspective-view illustrating the upper coil barand the lower coil bar disposed in position;

FIG. 7 is a cross sectional plan view of the upper coil bar and thelower coil bar disposed in a slot according to the first embodiment;

FIG. 8 is a schematic plan view illustrating the armature according tothe first embodiment;

FIG. 9 is a plan view illustrating an insulating spacer disposed at aside of the armature opposite brushes according to the first embodiment;

FIG. 10 is a cross-sectional side view illustrating a fixing cap;

FIG. 11 is a cross-sectional side view illustrating an insulation cap;

FIG. 12 is a winding chart of the armature according to the presentinvention;

FIG. 13 is a plan view illustrating an insulating spacer disposed at thebrush side of the armature according to the first embodiment;

FIG. 14 is a perspective view illustrating a variation of the upper coilbar according to the first embodiment;

FIG. 15 is a cross-sectional side view illustrating an armatureaccording to a second embodiment;

FIG. 16 is a cross-sectional side view illustrating a coil end portionof an armature according to a third embodiment;

FIG. 17 is a cross-sectional side view illustrating an armatureaccording to a fourth embodiment;

FIG. 18 is a schematic plan view illustrating the armature core plateaccording to the fourth embodiment;

FIG. 19 is a cross-sectional side view illustrating final bending of anupper coil bar according to a fifth embodiment;

FIG. 20 is a cross-sectional side view illustrating the upper coil barafter the final bending according to the fifth embodiment;

FIG. 21 is a cross-sectional side view illustrating final bending of anupper coil bar according to a variation of the fifth embodiment;

FIG. 22 is a cross-sectional side view illustrating the upper coil barafter the bending according to the variation of the fifth embodiment;

FIG. 23 is a cross-sectional side view illustrating a coil end portionof an armature according to a sixth embodiment; and

FIG. 24 is cross-sectional side view illustrating a coil end portion ofan armature according to a seventh embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiment will be described with reference to appendeddrawings hereafter.

First Embodiment

A rotary electric machine according to a first embodiment is describedwith reference to FIGS. 1 through 13 and FIG. 16.

The rotary electric machine 500 has a shaft 510, an armature core 520carried by the shaft 510, a yoke 501 and a stationary magnetic poles 550secured to the yoke 501, as illustrated in FIG. 1 and FIG. 2.

The shaft 510 is supported rotatably by a metal bearing 911 which isdisposed in an external member (not shown) and a metal bearing 921 whichis press-fitted into an inner periphery of an end frame 900. A front endof the shaft 510 has a gear which is engaged with a gear of a planetarygear unit of a starter motor (not shown).

The armature core 520 is composed of a plurality of stacked ring-shapedcore plates 521 having center opening 522, to which the shaft 510 ispress-fitted. The core plates 521 are produced from a thin steel sheetby punch pressing. A plurality of openings 523 are formed at centralportions of the core plate 521 around the center opening 522 to reduceweight. A plurality of slots 524 (25 slots for instance) are formedalong the outer periphery of the core plates to accommodate an armaturecoil 530. A plurality of Y-shaped tooth tips 525 are formed on bothsides of teeth which are formed between the slots as shown in FIG. 3.They are bent to hold the armature coils 530 in the slots and tointroduce field magnetic flux.

The armature coil 530 is composed of a plurality of upper coil bars (forinstance, 25 coil bars) 531 and the same number of the lower coil bars532. The upper coil bars 531 and the lower coil bar 532s are stacked inthe radial direction to form a double-layer coil type and are connectedat one end to other lower coil bars and upper coil bars in differentslots respectively to form a single-turn coil. FIG. 12 illustrates anexample of winding of the armature coil 530 and a reference numeral 910indicates one of the brushes in contact with the upper coil-end portions534 which are described later.

The upper coil bar 531 is made of copper or other conductive materialand is composed of an upper coil section 533 which extends in the slot524 in front of the stationary magnetic pole 550 and a pair of endsections 534 which extend radially inward from both ends of the uppercoil section 533, as shown in FIG. 6.

The upper coil section 533 is a bar-like member which has a rectangularcross section and is covered with an insulating film sheet 540a such asnylon thin film or paper, and is held in the slot securely with a lowercoil section 536 (to be described later) as shown in FIG. 7.

The pair of end sections 534 of the upper coil bar 531 are symmetricalin the shape. One of the pair of end sections is inclined in a rotatingdirection as schematically shown in FIG. 8, and the other is inclined inthe opposite direction as shown in FIG. 5. The inclined angle of thepair of the end sections relative to the radial direction is the same asthat relative to the upper section 533. One of the end section 534disposed at a side of the end frame 900 composes a commutator segment incontact with brushes 910 to be described later and, therefore, thesurface in contact with the brushes 910 is made smooth.

The upper coil-end sections 534 are disposed radially in parallel witheach other in a circular plane vertical to the shaft 510 to formparallel grooves 535 between the coil-end sections 534 and, therefore,they become wider as they go out from the center as schematically shownin FIG. 8. As a result, the contact surface of the coil ends with thebrushes can be provided much broader than that of the conventionalrotary electric machine so that heat generated by the brushes candissipate more effectively.

When the armature rotates, wind generated by the grooves 535 flows fromthe central portion toward radially outer portion of the upper coil-endsections 534. As a result, the heat generated by friction of the brush910 and the upper coil-end sections 534 is dissipated and the resultantpowder of the brush can be discharged sufficiently.

The upper coil-end section 534 has a small projection 534c which isdisposed at a radially outer portion thereof between the upper coil-endsection 534 and a lower coil-end section 537 as shown in FIG. 2, FIG. 4and FIG. 6 to retain an insulating spacer 560 or 560a by engagement withan opening 561 formed in the spacer for positioning shown in FIG. 9 andFIG. 13.

A narrow bar portion 533g and grooves 533f on the opposite sides areformed in the upper coil section 533 near the brush-side upper coil-endsection 534 as shown in FIG. 4.

The lower coil bar 532 is made of copper or other conductive materialand composed of a lower coil section 536 which extends in the slot 524and a pair of the end sections 537 which extend radially inward fromboth ends of the lower coil section 536. The lower coil bar 532 does nothave a narrow bar portion 533g or grooves 533f.

The upper coil-end sections 534 and the lower coil-end sections 537 areinsulated by the spacers 560 shown in FIG. 13 and the lower coil-endsections 537 and the armature core 520 are insulated by an insulatingring 590 made of resinous material such as nylon or phenolic resin asshown in FIG. 1.

The lower coil section 536 is a bar-like member which has a rectangularcross section and is covered with an insulating film sheet 541 such asnylon thin film or paper, and held in the slot securely with the uppercoil section 533 as shown in FIG. 6 and FIG. 7.

The lower coil-end sections 537 are disposed to incline in a directionopposite that of the upper coil-end sections 534. The angle ofinclination the pair of the lower end sections 537 relative to theradial direction is the same as that relative to the lower coil section536.

Radially inner ends of the lower coil-end sections 537 have lowerinternal extensions 539 at opposite sides as shown in FIG. 2. Each ofthe lower internal extensions 539 is inserted into a correspondingrecess formed in the central opening of the insulating spacer 560 or560a under each corresponding extension 538 (to be described later) ofthe upper coil-end sections 534 as shown in FIG. 9 and FIG. 13. Thelower internal extensions 539 are spaced from and insulated from theshaft.

Radially inner ends of the upper coil-end section 534 have upperinternal extensions 538 at the opposite sides as shown in FIG. 2. Eachof the upper internal extensions 538 is placed on a correspondingextension 539 of the lower coil-end sections 537 and bonded thereto byway of welding or a mechanical element. As a result, the upper and lowerinternal extensions 538 and 539 of both sides of the upper and lowercoil sections 533 and 536 compose rings as shown in FIG. 8. A pair offixing caps 570, each of which has an outer ring 571 for retaining theextensions and an inner ring 572 for receiving the shaft as shown inFIG. 10, are press-fitted to the shaft and hold the outer peripheries ofthe ring shaping upper internal extensions 538 via insulating caps 580shown in FIG. 11, as shown in FIG. 1.

The insulating spacers 560 for the brush side of the armature and 560afor the opposite side thereof are thin rings made of resinous materialsuch as epoxy resin, phenolic resin or nylon, and have a plurality ofopenings 561 to be engaged with the projections 534c of the uppercoil-end sections 534 as shown in FIG. 9 and FIG. 13. The insulatingspacer 560 has a toothed central opening which has recesses 562accommodating the lower internal extensions of 539 and teeth 562a. Theopenings 561, the recesses 562 and the teeth 562a are used forpositioning of the armature coil 530. The insulating spacer 560 hasteeth 563 on the outer periphery thereof, which are engaged with thenarrow bar portions 533g.

The openings 561 can be made when the upper coil-end section 534 ispunched from the outside against the insulating spacer 560 to form theprojections 534c. In this case, the upper coil-end section is hardeneddue to the plastic deformation so that the abrasion caused by contactwith the brush 910 can be reduced.

The fixing cap 570 is a steel ring, which has the outer ring 571 and theinner ring 572 (as described before) and a retaining ring 573 whichprevents the upper coil-end sections 534 from shifting axially. Theouter ring 571 prevents the armature coil from expanding because of thecentrifugal force.

The fixing cap 570 disposed in front of the armature 540 in abutmentwith a front plate 800 prevents the armature 540 from moving in theaxial direction with the fixing cap 570 disposed in the rear of thearmature 540 in abutment with the end frame 900. Thus, no additionalretaining member for the armature is necessary.

In summary, the upper coil bars 531 and the lower coil bars 532 areretained in the slots 524 by the tooth tips 525 as shown in FIG. 7 andsecured in position by the openings 561 and recesses 562 of theinsulating spacers 560 and 560a shown in FIG. 9 and FIG. 13, and also bythe fixing caps 570 shown in FIG. 10.

The upper coil sections 533 and the lower coil sections 536 are disposedin the slots 524 of the armature core 520, and the tooth tips 525 arebent down as indicated by arrows shown in FIG. 7 so that the upper coilsections 533 and the lower coil sections 536 are prevented fromprojecting from the slots 524. The upper coil section 533 is coveredwith both lower insulating film sheet 540a and upper insulating filmsheet 541 so that the insulation of the upper coil section 533 may beprotected even if the tooth tip 525 presses the upper coil section hard.

Each of the lower internal extensions 539 of the lower coil-end sections537 is fitted to each of the recesses 562 of the insulating spacer 560so that the lower coil end sections are disposed in position andretained against the centrifugal force. Each of the openings 561 of theinsulating spacer 560 receives a small projections 534c to position theupper coil-end sections 534 and prevents them from expanding due to thecentrifugal force.

The fixing cap 570 holds the upper internal extensions 538 and the lowerinternal extensions 539 from the outside so that inner portions of thearmature coil 530 can be prevented from expanding. The fixing cap 570also restricts axial movement of the upper internal extensions 538 andthe lower internal extensions 539 so that additional space for allowingthe axial movement is not required and the axial length of the startercan be reduced.

Each of the narrow bar portions 533g formed on the brush side of theupper coil sections 533 engages each of the teeth 563 on the outerperiphery of the insulating spacer 560. The width of the narrow portion533 is approximately the same as the thickness of the insulating spacer560. Thus, the axial movement of the brush-side upper coil sections 534is controlled to maintain the commutating surface formed by thebrush-side upper coil-end sections 534 smooth even if the upper coilsections 533 thermally expand, so that good commutation can be ensured.

In order to further ensure good commutation, the lower internalextensions 539 have grooves 539a on their cylindrical upper surfaces asshown in FIG. 16. The width of the groove 539a is approximately equal tothe thickness of the insulating spacer 560. The teeth 562a formed on thetoothed central opening of the insulating spacer 560 are fitted into thegrooves 539a. As a result, axial and circumferential movement of thelower coil-end sections 537 and the upper coil-end sections 534 weldedtogether can be restricted even if the armature coil is heated orsubjected to high temperature.

Since the upper coil-end sections and the lower coil-end sections areconnected in a unit at their internal extensions 538 and 539 via theinsulating spacer 560, accuracy and mechanical strength includingstrength against the centrifugal force can be ensured, and also a goodheat path from the upper coil-end sections 534, through the insulatingspacers 560 and 560a and the lower coil-end sections 537, to thearmature core 520 can be formed without using a complicated structure.

When the armature is assembled, the shaft 510 is press-fitted into thearmature core 520 having a plurality of the stacked core plates 521, andthe insulating rings 590 are disposed on both sides of the armaturecore.

Then, the lower coil sections 536 of the lower coil bars 532 areinserted into the slots 524 with the insulating film sheet 541 and theinsulating spacer 560 is put on the outer surfaces of the lower coil-endsections 537 so that the lower extensions 539 are respectively fitted tothe recesses 562 of the central opening of the insulating spacer 560.Thus, the positioning of the lower coil bars is finished.

Thereafter, the upper coil sections 533 are inserted into the slots 524with the upper insulating film sheets 540 respectively, and theprojections 534c of the upper coil-end sections 534 are fitted into theopenings 561 respectively. Thus, the positioning of the upper coil barsis finished. The upper internal extensions 538 and the lower internalextensions 539 are subsequently bonded together by welding or the like.

Then, the tooth tips 525 are bent down to hold the upper and lower coilsections 533 and 536 in the slots 524 and the fixing caps 570 arepress-fitted to the shaft 510 from both ends thereof to cover and holdthe upper internal extensions 538 of the armature coil 530. Thus, thearmature coil 540 is assembled.

The stationary magnetic poles 550 include permanent magnets which aredirectly secured to the yoke 501. The permanent magnets can be replacedwith field coils energized by a battery or a generator in a well-knownmanner.

Brush holders 920 are secured to the end frame 900 which is secured toone end of the yoke 501. They accommodate the brushes 910 slidably inthe axial direction and springs 930 which bias the brushes against theupper coil-end sections 534.

Variations of the First Embodiment

Through holes can be formed in the yoke 501 so that the brush powdercaused by the brush wear can be discharged with cooling wind generatedby the centrifugal fan function of the armature, thereby ensuringinsulation of the armature coil 540.

Narrow bar portions 533g formed in the upper coil sections 533 can bereplaced with projections 533h formed on both sides of thereof bypunching or the like. In this case, the outer recess 563 is fittedbetween the upper coil-end section 534 and the projection 533h.

Resinous binder can be filled into the space between the insulatingspacer 560 and the upper coil-end sections 534 after the insulationspacer 560 is put between the lower coil-end sections 537 and the uppercoil-end sections 534 so as to secure the upper coil-end sections to theinsulating spacer 560. The insulating spacer 560 can be molded withresinous material after the lower coil-end sections 537 and the uppercoil-end sections 534 are assembled. The resinous binder can be put onlyin a space around the upper coil-end section 534. Since the movement ofthe coil is allowed in the direction opposite the brush, the surface ofthe upper coil-end section can be kept more smooth.

Even a conductive plate can be used in place of the insulating plate 534if the lower and upper coil-end sections are coated with insulatingmaterial. In this case, the conductive plate functions to hold thearmature coil in place as described before.

The narrow bar portions 533g can be omitted when the fixing cap 570retains the upper coil-end sections in position securely.

The fixing cap 570 can be made of resilient material such as springsteel. If the upper coil-end sections 534 expand thermally, the shift isabsorbed by the resiliency of the fixing cap 570 and the smooth surfacesof the commutating portions of the upper coil-end sections 534 areensured without the cap's shifting on the shaft 510.

Second Embodiment

A rotary electric machine according to a second embodiment is describedwith reference to FIG. 15. Reference numerals which are the same asthose used in the description related to the first embodiment indicatethe same or substantially the same parts or portions. Therefore, onlydifferent parts and portions of different embodiments are describedhereinafter.

In order to distinguish the brush side members from the other sidemembers in this embodiment, a prime mark (') is put on the correspondingparts or portions of the other side (hereinafter referred to as second)members.

Fixing caps 570 and 570' are press-fitted to a shaft 510 from theoutside to retain the upper coil-end sections 534 and 534' and the lowercoil-end sections 537 and 537' in position in the same manner as thefirst embodiment.

However, a second insulating cap 580' is bonded to the armature-sidesurface of the fixing cap 570' by adhesive material. The secondinsulating cap 580' has an outer ring portion (which is the same as inthe first embodiment) which faces the second upper coil-end sections534' at a small axial gap Δd. The axial gap Δd allows the thermalexpansion of the upper and lower coil sections so that the commutationsurface formed by the brush-side upper coil-end sections can be keptsmooth even if the temperature of the upper coil-end sections 534 andthe upper coil sections 534 becomes high.

The second upper coil-end 534' has small projections 534c', which arealso substantially the same as those of the first embodiment; however,they are longer than the gap Δd so that they cannot get out of openings561' (the same as those of the first embodiment) of the secondinsulating spacer 560' even if the thermal expansion is significant.

The fixing caps 570 and 570' can be secured to the armature coredirectly. In this case, the gap Δd should be made longer than differenceof the thermal expansion between the armature core 520 and the upper andlower coil sections 533 and 536.

The small projections can be formed on the upper coil-end sections 534and 534' to be engaged with openings which are formed in the insulatingspacers 560 and 560' . The insulating spacer 560 and 560' can be madefrom materials other than insulating material. For instance, metalplates covered with insulation coating can be used.

Third embodiment

A rotary electric machine according to a third embodiment of the presentinvention is described with reference to FIG. 16. In this embodiment,grooves 533i are formed on the inner peripheries of the upper coilsections 533 to accommodate the peripheral portions of the insulatingspacer 560 along with grooves formed on the lower internal extensions536 in the same manner as described with regard to the first embodiment.

Accordingly, the commutation surface of the upper coil-end sections canbe maintained smooth.

Fourth Embodiment

A rotary electric machine according to a fourth embodiment of thepresent invention is described with reference to FIG. 17 and FIG. 18.The machine according to this embodiment is almost the same except foran armature core 520a.

The armature core 520a has through holes 523a and 523b which aredifferent from those of the first embodiment. That is, the through holes523a are disposed in a circular zone in the armature core 520a havinginside diameter d1 which is greater than the outside diameter D1 of theouter ring 571 of the fixing cap 570, and the through holes 523b aredisposed in a circular zone having outside diameter d2 which is smallerthan the inside diameter of the outer ring 571 of the fixing cap 570 asshown in FIG. 17. The inside diameter d1 is the shortest distancebetween the through holes 523a, that is, between the innermost portionsof the through holes 523a and the outside diameter is the longestdistance between through holes 523b, that is, between the outermostportions of the through holes 523b.

Thus, the end surface of the outer ring 571 presses against the portionbetween the above two zones so that the upper coil-end sections may notbend, thereby keeping the commutating surface of the upper coil-endsections smooth.

Even if the upper coil-end sections 534 expands thermally, the uppercoil-end sections are prevented from bending into the through holes.

Fifth Embodiment

A rotary electric machine according to a fifth embodiment of the presentinvention is described with reference to FIG. 19 and FIG. 20. In thisembodiment, the upper coil sections 533 are not completely bent beforethey are inserted into the slots 524 as shown in FIG. 19. The upper coilsections 533 have the same grooves 533i as those of the third embodimentto which the outer peripheral portion of the insulating spacer 560 isfitted; however, the grooves 533i are formed by punching in thisembodiment. The outer diameter of the insulating spacer 560 is madelarger than the outer diameter of the lower coil sections 536.

The upper coil-end sections 534 are bent and the projections 534c areinserted into the openings 561 of the insulating spacer 560. Finally,the lower internal extensions 539 and the upper coil-end sections arewelded to finish the armature coil 530.

A variation of the fifth embodiment is shown in FIG. 21 and FIG. 22.

In this embodiment, the upper coil-end sections 534 have toothedsurfaces on the portions in abutment with the insulating spacer 560 soas to increase the bonding strength of the upper coil-end sections andthe insulating spacer 560, thereby preventing shifting of the uppercoil-end sections 534 in the radial, circumferential and axialdirections.

Sixth Embodiment

A rotary electric machine according to a sixth embodiment of the presentinvention is described with reference to FIG. 23.

An elastic member 579 is disposed between the fixing cap 570 and theupper coil-end sections 534 in this embodiment. Since the elastic memberbiases the upper coil-end sections elastically, the thermal expansion ofthe upper and lower coil portions can be absorbed by the elastic member579. The elastic member 579 can be formed separately or integrally.

Seventh Embodiment

A rotary electric machine according to a seventh embodiment of thepresent invention is described with reference to FIG. 24.

An elastic spacer 600 is disposed between the lower coil-end sections537 and the insulating ring 590. The insulating ring 590 and the elasticspacer 600 can be formed in a unit. The elastic ring 600 absorbs thethermal expansion effectively in this case. The elastic member 579 ofthe sixth embodiment can be also provided in this embodiment.

Although the present invention has been fully described in connectionwith the preferred embodiment thereof with reference to the accompanyingdrawings, it is to be noted that various changes and modifications willbecome apparent to those skilled in the art. Such changes andmodifications are to be understood as being included within the scope ofthe present invention as defined by the appended claims.

What is claimed is:
 1. A rotary electric machine comprising:a shaft; anarmature core connected to said shaft, a plurality of slots beingdefined on an outer periphery of said armature core; a plurality ofpairs of upper coil sections and lower coil sections, each said pairbeing disposed in a corresponding one of said slots; a plurality oflower coil-end sections, each having one end connected to an end of acorresponding end of said lower coil section and extending toward saidshaft; a plurality of upper coil-end sections, each being connectedbetween an end of one of said upper coil sections and another end of acorresponding one of said lower coil-end sections and extending towardsaid shaft to form a smooth contact surface; a brush member disposed incontact with contact surfaces composed of said upper coil-end sections;and structure disposed on said shaft axially outside of said upper coilend sections, said structure resiliently retaining said upper coil endsection from outside, thereby allowing thermal expansion of said upperand lower coil sections while maintaining said smooth contact surface;wherein said structure comprises a fixing cap made of a resilient steeland externally biasing said upper coil-end sections against saidarmature core, and wherein said fixing cap includes an inner ring fittedon said shaft, an outer ring pressing said upper coil-end sectionstoward said armature core, and a retaining ring connecting said innerring and said outer ring.
 2. A rotary electric machine as claimed inclaim 1, said upper coil sections and lower coil sections are connectedrespectively with said upper coil-end sections and lower coil-endsections.
 3. A rotary electric machine as claimed in claim 1, whereineach pair of said lower coil sections and said lower coil-end sectionsare integrated and each pair of said upper coil sections and said uppercoil-end sections are integrated.
 4. A rotary electric machine asclaimed in claim 1, further comprising an elastic spacer disposedbetween said lower coil-end section and said armature core, therebyabsorbing thermal expansion in the axial direction.
 5. A rotary electricmachine as claimed in claim 1, further comprising an insulating spacerdisposed between said upper coil-end sections and said lower coil-endsections.
 6. A rotary electric machine comprising:a shaft; an armaturecore connected to said shaft, a plurality of slots being defined on anouter periphery of said armature core; a plurality of pairs of uppercoil sections and lower coil sections, each said pair being disposed ina corresponding one of said slots; a plurality of lower coil-endsections, each having one end connected to an end of a corresponding endof said lower coil section and extending toward said shaft; a pluralityof upper coil-end sections, each being connected between an end of oneof said upper coil sections and another end of a corresponding one ofsaid lower coil-end sections and extending toward said shaft to form asmooth contact surface; a fixing cap disposed on said shaft axiallyoutside of said upper coil end sections and resiliently retaining saidupper coil end section from outside, thereby allowing thermal expansionof said upper and lower coil sections while maintaining said smoothcontact surface, wherein said fixing cap is made of a resilient steeland disposed at a side opposite said armature core to bias said uppercoil-end sections, said fixing cap including an inner ring fitted onsaid shaft, an outer ring pressing said upper coil-end sections towardsaid armature core, and a retaining ring connecting said inner ring andsaid outer ring.